Castlevania Portrait of Ruin Credits Glitching

Hello.

Castlevania PoR runs overall very well on DeSmuME 0.9.10 x 64 (Windows 10). But the end credits are extremely glitchy. They flicker back and forth between the upper and lower screens, even duplicating the words between the screens (normal credits scroll from bottom up to the top).

For streaming purposes, I currently have the orientation set to Horizontal, Main Screen First.

If someone could please advise on a possible fix for this, I would be very appreciative.